Ownership Interest in Subsidiary, Percent

No definition available.

Name:	bkfs_OwnershipInterestinSubsidiaryPercent
Namespace Prefix:	bkfs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period after which Co-Investors will have Put Rights

+ References

No definition available.

+ Details

Name:	bkfs_PeriodafterwhichCoInvestorswillhavePutRights
Namespace Prefix:	bkfs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period after which Company will have Call Rights on Ownership Interests in Subsidiary

+ References

No definition available.

+ Details

Name:	bkfs_PeriodafterwhichCompanywillhaveCallRightsonOwnershipInterestsinSubsidiary
Namespace Prefix:	bkfs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfEquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=bkfs_CollateralAnalyticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=bkfs_OptimalBlueLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=bkfs_CannaeHoldingsInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=us-gaap_CoVenturerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=bkfs_MinorityCoInvestorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=bkfs_ThomasH.LeePartnersLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Business Acquisition - Narrative (Details) - USD ($) $ in Millions			3 Months Ended	6 Months Ended
	Jul. 26, 2020	Mar. 03, 2020	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Business Acquisition [Line Items]
Equity interests acquired						18.10%
Proceeds from sale of interest in to-be-formed subsidiary				$ 8.4	$ 0.0
Collateral Analytics
Business Acquisition [Line Items]
Total purchase price consideration		$ 51.0
Equity interests acquired		100.00%
Subsequent Event \| Optimal Blue, LLC
Business Acquisition [Line Items]
Total purchase price consideration	$ 1,800.0
Forecast
Business Acquisition [Line Items]
Ownership Interest in to-be-formed subsidiary (percent)			60.00%
Period after which the company will have call rights on ownership interests in the newly formed subsidiary			3 years
Period after which co-Investors will have put rights for ownership interests in newly formed entity			3 years
Cannae Holdings, Inc. [Member] \| Co-venturer \| Forecast
Business Acquisition [Line Items]
Equity ownership commitment in to-be-formed new subsidiary (percent)			20.00%
Proceeds from sale of interest in to-be-formed subsidiary			$ 290.0
Minority Co-Investors [Member] \| Forecast
Business Acquisition [Line Items]
Equity ownership commitment in to-be-formed new subsidiary (percent)			40.00%
Proceeds from sale of interest in to-be-formed subsidiary			$ 580.0
Thomas H. Lee Partners, LP [Member] \| Co-venturer \| Forecast
Business Acquisition [Line Items]
Equity ownership commitment in to-be-formed new subsidiary (percent)			20.00%
Proceeds from sale of interest in to-be-formed subsidiary			$ 290.0